1. Field of the Invention
The present invention generally relates to a system for processing a wafer, and more particularly to a wafer bake system.
2. Description of the Related Art
In a conventional semiconductor fabrication process, a semiconductor element pattern is formed on a wafer by a series of steps of depositing a photoresist layer on the wafer, supplying light to the photoresist layer and developing the photoresist layer, and then the wafer is baked before and after the above-described steps. The wafer is deformed depending on process systems, photoresist solutions and processing methods. As more large-sized wafers are needed, deformation of the wafer is a major problem in the production of the wafer. When the deformed wafer is baked, a proximity gap between the wafer and a heating plate is not uniform, thereby generating a temperature gradient in the wafer. The temperature gradient causes critical dimensional problems on the wafer. The critical dimensions refer to the minimum line width reproduced on the wafer when the shape of a mask is copied onto the wafer.
Accordingly, a wafer bake system for preventing the temperature gradient in the wafer is required. Thus, several aspects must be considered when the wafer bake system is designed. When the structure of the heating plate is modified, it is difficult to obtain uniform thermal transfer. Further, the contact between the heating plate and the wafer causes contamination on the wafer and differences in temperature in the region between contact and non-contact portions of the heating plate and the wafer.
However, the conventional wafer bake system is disadvantageous because it can't effectively prevent non-uniform temperature gradient in the wafer.